/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.beam.runners.spark.translation;

import java.util.Collections;
import java.util.Iterator;
import org.apache.beam.sdk.transforms.join.RawUnionValue;
import org.apache.beam.sdk.values.WindowedValue;
import org.apache.spark.api.java.function.FlatMapFunction;

@SuppressWarnings({
  "nullness" // TODO(https://github.com/apache/beam/issues/20497)
})
class SparkExecutableStageExtractionFunction<OutputT>
    implements FlatMapFunction<RawUnionValue, WindowedValue<OutputT>> {
  private final int unionTag;

  SparkExecutableStageExtractionFunction(int unionTag) {
    this.unionTag = unionTag;
  }

  @Override
  public Iterator<WindowedValue<OutputT>> call(RawUnionValue rawUnionValue) {
    if (rawUnionValue.getUnionTag() == unionTag) {
      WindowedValue<OutputT> output = (WindowedValue<OutputT>) rawUnionValue.getValue();
      return Collections.singleton(output).iterator();
    }
    return Collections.emptyIterator();
  }
}
